fighting against a virus is fighting a biological enemy; fighting against the Russians, the Chinese, or the terrorists is fighting a cultural enemy. But fighting against the Giselians is fighting both of them, with the difference we know nothing about their culture or civilization, nor about their biology.

By now we know the descendants of these invaders who fall behind the leading edge retain their ancestor’s preferences. These descendants focus on pursuing the invasion wave as quickly as possible, devastating whatever civilization they may encounter along their path, rather than staying behind to build stable long-lasting civilizations.